1. Field of the Invention
The present invention relates to lifting apparatus and accessories, and more particularly to an improved spreader bar lifting apparatus for use with cranes and other lifting devices that use slings. Even more particularly the present invention relates to an improved multi-part spreader bar arrangement that includes a plurality of connectable sections including at least a pair of bar sections and a pair of end members, and wherein the detachable connections between the sections are provided with annular load bearing faces that carry a majority of the axial compressive load during use.
2. General Background of the Invention
Spreader bars are commonly used in industry for lifting large objects with a single hook that is attached to the crown block and lift cables of a crane. A lifting hook is commonly provided with a pair of slings that depend from the crane hook at angles in a bridle fashion, each of the slings connecting to an end portion of the spreader bar. Parallel, depending lift lines are then suspended from the end portions of the spreader bar downwardly to the load that is to be lifted. An example of a spreader bar that has been patented can be seen in my prior U.S. Pat. No. 4,397,493, and entitled "Spreader Bar Assembly".
One of the problems with spreader bars is that of sizing the spreader bar to meet a particular load. Some devices have attempted to provide telescoping sections in order to adjust the spreader bar to different lengths so as to accommodate different loads. Such a telescoping, locking spreader bar operates well for relative light loads of a few thousand pounds. However, in the lifting of extremely heavy objects such as, for example, 25-50 tons, a much more rugged construction is required.
Another problem that faces the user of a spreader bar is that of transporting the bar from one place to another at a construction facility, fabrication yard, plant, shop, or the like. Most spreader bars are extremely heavy when compared to the strength of an average worker. To lift a very heavy object, one has typically needed a very heavy spreader bar. This creates a hazardous condition when workers attempt to move a very heavy spreader bar from one location to another.